FUNCTIONAL BLOCK DIAGRAM

REV. A

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a

Low Cost Signal

Conditioning 8-Bit ADC

AD670

FEATURES

Complete 8-Bit Signal Conditioning A/D Converter

Including Instrumentation Amp and Reference

Microprocessor Bus Interface

10

s Conversion Speed

Flexible Input Stage: Instrumentation Amp Front End

Provides Differential Inputs and High Common-Mode

Rejection

No User Trims Required

No Missing Codes Over Temperature

Single +5 V Supply Operation

Convenient Input Ranges

20-Pin DIP or Surface-Mount Package

Low Cost Monolithic Construction

MIL-STD-883B Compliant Versions Available

GENERAL DESCRIPTION

The AD670 is a complete 8-bit signal conditioning analog-

to-digital converter. It consists of an instrumentation amplifier

front end along with a DAC, comparator, successive approxima-

tion register (SAR), precision voltage reference, and a three-

state output buffer on a single monolithic chip. No external

components or user trims are required to interface, with full

accuracy, an analog system to an 8-bit data bus. The AD670

will operate on the +5 V system supply. The input stage pro-

vides differential inputs with excellent common-mode rejection

and allows direct interface to a variety of transducers.

The device is configured with input scaling resistors to permit

two input ranges: 0 mV to 255 mV (1 mV/LSB) and 0 to 2.55 V

(10 mV/LSB). The AD670 can be configured for both unipolar

and bipolar inputs over these ranges. The differential inputs and

common-mode rejection of this front end are useful in applica-

tions such as conversion of transducer signals superimposed on

common-mode voltages.

The AD670 incorporates advanced circuit design and proven

processing technology. The successive approximation function

is implemented with I

SiCr resistors provide the stability required to prevent missing

codes over the entire operating temperature range while laser

wafer trimming of the resistor ladder permits calibration of the

device to within

±1 LSB. Thus, no user trims for gain or offset

are required. Conversion time of the device is 10

µs.

The AD670 is available in four package types and five grades.

The J and K grades are specified over 0

°C to +70°C and come

in 20-pin plastic DIP packages or 20-terminal PLCC packages.

The A and B grades (–40

°C to +85°C) and the S grade (–55°C

to +125

°C) come in 20-pin ceramic DIP packages.

One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.

Tel: 617/329-4700

Fax: 617/326-8703

The S grade is also available with optional processing to

MIL-STD-883 in 20-pin ceramic DIP or 20-terminal LCC

packages. The Analog Devices Military Products Databook

should be consulted for detailed specifications.

PRODUCT HIGHLIGHTS

1. The AD670 is a complete 8-bit A/D including three-state

outputs and microprocessor control for direct connection to

8-bit data buses. No external components are required to

perform a conversion.

2. The flexible input stage features a differential instrumenta-

tion amp input with excellent common-mode rejection. This

allows direct interface to a variety of transducers without

preamplification.

3. No user trims are required for 8-bit accurate performance.

4. Operation from a single +5 V supply allows the AD670 to

run off of the microprocessor’s supply.

5. Four convenient input ranges (two unipolar and two bipolar)

are available through internal scaling resistors: 0 mV to

255 mV (1 mV/LSB) and 0 V to 2.55 V (10 mV/LSB).

6. Software control of the output mode is provided. The user

can easily select unipolar or bipolar inputs and binary or 2s

complement output codes.